The present invention relates generally to copy protection. More specifically, the present invention relates to a method and apparatus for providing copy protection to recorded and broadcast data. The present invention applies to video, audio and other types of data recorded on a medium or broadcast to an audience.
With the proliferation of digital recording, the ability to create unauthorized copies of digitally recorded content has become a serious problem for those that have a vested interested in the content. Copyright laws prohibit the unauthorized copying of copyrighted materials. However, copyright laws seldom prevent individuals from unauthorized copying.
Current copy protection schemes typically only provide copy protection to digital content stored on a recording medium, such as a Digital Video Disc (DVD) disc (sometimes also referred to as digital versatile disc). FIG. 1 illustrates a conventional copy protection scheme 10. The copy protection scheme includes a host computer 20, a DVD drive 14 which reads data from a DVD disc 12.
In the copy protection scheme illustrated in FIG. 1, DVD drive 14 is capable of reading DVD disc 12 and passing the data to host computer 20. If the DVD disc 12 is copy protected according to a CSS (Content Scrambling System) scheme, the drive will insist on undergoing an authentication protocol with the host 20 before transferring the scrambled data. The scrambled data may only be unscrambled if the xe2x80x9cdisc keyxe2x80x9d and the xe2x80x9ctitle keyxe2x80x9d are known.
Knowledge of a xe2x80x9cglobal keyxe2x80x9d is necessary to perform the authentication and the exchange of the xe2x80x9cdiscxe2x80x9d and xe2x80x9ctitlexe2x80x9d keys. The xe2x80x9cglobal keyxe2x80x9d is incorporated in drives and in CSS compatible host systems in protected modules such that a user cannot easily obtain access to the xe2x80x9cglobal keyxe2x80x9d. The xe2x80x9cglobal keyxe2x80x9d allows the host to participate in the xe2x80x9cauthenticationxe2x80x9d step, which precedes the transfer of the descrambling keys and the scrambled data. Generally, the xe2x80x9cglobal keyxe2x80x9d is kept confidential among manufacturers to avoid proliferation of the xe2x80x9cglobal key.xe2x80x9d
After the authentication protocol has been completed, drive 14 will read disc 12 and obtain xe2x80x9ctitle keysxe2x80x9d from a region of the disc which is not accessible to the host, and pass these keys in encrypted form to host 20. The components of the host system 20, which are CSS compliant, are able to decrypt these keys and use the information to descramble the audio/video data subsequently retrieved from the disc.
In this way the CSS scheme prevents easy copying of the data on the disc because xe2x80x9cglobal keysxe2x80x9d are necessary to decrypt the descrambling keys, which are necessary to make any sense out of the data, and because the data is passed through user accessible busses only in scrambled form. If a copy of the scrambled data is made, the descrambling keys will be missing.
Copying the descrambled data is made difficult by various techniques, primarily keeping the data off user accessible busses. CSS compliant systems are obligated to inhibit copying of the CSS protected DVD video data. However, CSS encoding does not address the issues of broadcast data and the requirement that the end user be allowed to make a copy for time shifting purposes.
CSS encoding of digital data prevents the unauthorized copying of data stored on a physical medium. However, CSS encoding does not function for content that is broadcast over terrestrial radio frequencies or cable. FIG. 2 illustrates a typical television broadcast communication system. A transmitter 30 transmits audio, video, and/or information data over radio frequencies to an antenna 33. A typical home viewer may possess a set top box 40, a monitor 42, and recording devices 50 and 60.
Antenna 33 receives the data transmitted by transmitter 30 and provides it to set top box 40. Set top box 40 typically demodulates and/or decodes the data transmitted by transmitter 30 and provides a suitable data stream for viewing and/or recording to recorder 50 and monitor 42. A viewer may watch the decoded television signals on monitor 42, or the viewer may wish to record the transmission on recorder 50.
Currently, copyright laws permit a viewer to make a single copy of a transmission for time shifting purposes. That is, a viewer may not be home to view a particular transmission, therefore the viewer may wish to record the transmission and view it at a later time. A consistent problem that has faced broadcasters and content providers is that there is typically nothing to stop a viewer from making multiple generation copies of a transmission. Whether the transmission is broadcast over the airways or through a cable a viewer typically has the ability to make more than one copy of the transmitted content.
Referring back to FIG. 2, the viewer may record the transmitted data on disc 52 using recorder 50. At the same time the viewer may also record the data on disc 63 using recorder 60. Using either one of disc 52 or disc 63 viewer may make an infinite number of copies of the transmitted data.
Currently, copy protection schemes have been utilized to prevent copying of data stored on a medium. However, copy protection schemes typically do not provide copy protection for data that is transmitted. Therefore, there is a need to provide a copy protection scheme that allows a viewer to make one copy of a transmission, but which also prevents further copying after the initial copy is made. Further, the copy protection scheme should also prevent copying of data stored on a recording medium.
The present invention provides methods and apparatuses of copy protection that utilize a watermark and a permission key. The present invention can provide single-copy copy protection in addition to different levels of copy protection. The permission key and the watermark can also permit the invention to yield variable levels of copy protection.
In one embodiment, content including a watermark is transmitted to a recipient. The recipient is allowed to read the content but not record the content unless the recipient possesses a permission key. In a still further embodiment, the permission key is transmitted along with the content to permit recording. In another further embodiment, the permission key is a disposable permission key such that the permission key is not recorded and subsequent copies are prohibited. Alternately, the permission key is provided to the recipient at a different time to permit recording. In a still further embodiment, the permission key may be variable, wherein the permission key changes and the content requires more than one permission key.
In another embodiment, a copy protection compatible recording device is disclosed. The recording device is permitted to record a content including a watermark if a permission key is provided. The recording device includes a controller and a recording mechanism. The controller extracts a watermark from the content. When a watermark indicating that the content is copy protected, the controller must receive a corresponding permission key in order to allow the recording mechanism to record the content on a recording medium.
If a further embodiment, a copy protection compatible receiver is disclosed. The receiver includes a decoder, a permission key extractor, a decompressor and an interface. The decoder receives transmitted content including a watermark, and a permission key. The permission key extractor separates the permission key from the content. The interface receives the permission key and the content, separately, and provides them to a copy protection compatible recording device. The decompressor also receives the content without the permission key and decompresses the content, if necessary.
The use of a permission key and a watermark provides a versatile method of copy protecting content. The present invention provides copy protection that allows a recipient to make a single copy of the content, but prevents further copying of the content. Also, other levels of copy protection are supported by the use of permission keys and watermarks.
One advantage of the present invention is that playback control is not required. Without playback control watermark detection is not required of the playback devices.